M4A4 - Heartbeat was created through the use of a unique pattern depicting a heart icon with highlighted contours in silver lines.

Advanced settings were also used, such as:

1) The texture of the normal map, where a marble pattern with a white tint was used, which gives the overall pattern shine and radiance.

2) Ambient occlusion effect using a fractal pattern on a dark background.

Please give feedback in the comments. Tell me what you think, do you like it, would you like to see this skin in the future. Also let me know what you would change and how you would do it.